Re: r3000 instruction set

["Steven J. Hill" <sjhill@realitydiluted.com>]

Kevin D. Kissell wrote:
> 
> The 3900 family should run MIPS I code compiled for the R3000.
>
Yep.

> The 3912 has no FPU, but if you're running on any contemporary
> MIPS/Linux kernel and library system, you neither need nor want
> soft-float.  The kernel does FP instruction emulation.  Running soft-float
> would make for faster, if larger, code, but requires that the whole
> system, particularly glibc, be built for soft-float, which is rarely done
> (and the last time I tried it, didin't quite work with the standard
> glibc sources out-of-the-box). 
> 
Correct. I use the FP emulator in Linux for my TX3917/PR31700 stuff. I
have had no problems. Current glibc has assembly code that assumes hardware
floating point which is why building for soft-float does not work out of
the box. There are probably some patches out there to rectify that. My
personal choice, use uClibc (http://uclibc.org/) for your C runtime. I wrote
the dynamic linker loader for MIPS and would highly recommend you try it out.
I would really like to see more testing of it.

Also, I have some documents for the 3912 on my FTP site:

    ftp://ftp.realitydiluted.com/docs/Toshiba
    ftp://ftp.realitydiluted.com/docs/Philips

It should be noted that the Toshiba TX3912 and the Philips PR31700 are
identical cores. There was definitely some cross-licensing going on there.
Perhaps Kevin or Dominic would know this in more detail, but it is not
really that important.

-Steve